Switching From Reactant to Substrate Engineering in the Selective Synthesis of Graphene Nanoribbons

TL;DR

This paper introduces a substrate-guided approach for synthesizing atomically precise graphene nanoribbons, expanding beyond traditional precursor-based methods by utilizing nanotemplated surfaces to control GNR formation.

Contribution

It demonstrates how substrate nanotemplating can direct GNR synthesis with atomic precision, combining self-assembly with substrate patterning for the first time.

Findings

Stepped Au(322) substrates enable selective 6-atom-wide armchair GNR synthesis.

Electronic properties of GNRs characterized by spectroscopy and DFT calculations.

Substrate patterning influences GNR width and structure.

Abstract

The challenge of synthesizing graphene nanoribbons (GNRs) with atomic precision is currently being pursued along a one-way road, based on the synthesis of adequate molecular precursors that react in predefined ways through self-assembly processes. The synthetic options for GNR generation would multiply by adding a new direction to this readily successful approach, especially if both of them can be combined. We show here how GNR synthesis can be guided by an adequately nanotemplated substrate instead of by the traditionally designed reactants. The structural atomic precision, unachievable to date through top-down methods, is preserved by the self-assembly process. This new strategy s proof-of-concept compares experiments using 4,4 -dibromo-para-terphenyl as molecular precursor on flat Au(111) and stepped Au(322) substrates. As opposed to the former, the periodic steps of the latter drive the selective synthesis of 6 atom-wide armchair GNRs, whose electronic properties have been further characterized in detail by scanning tunneling spectroscopy, angle resolved photoemission and density functional theory calculations.